1. Field of the Invention
The present invention relates to a manufacturing method of an optical waveguide, and especially relates to a manufacturing method of an optical waveguide for transmitting an optical signal between a luminous source and an optical receiver.
2. Description of the Related Art
In recent years and continuing, improvements in the speed of data communications are attained, and an electrical signal is converted into an optical signal that is transmitted using light as a medium of the data communication. In such an optical communications field, it is necessary to convert an electrical signal into an optical signal, and vice versa; and to modulate the light. For this purpose, various optical modules are used. Although there are various optical modules, the optical modules are fundamentally constituted by an optical waveguide on a substrate on which a luminous source (a vertical resonance laser, etc.) and an optical receiver (a photo diode, etc.) are arranged.
FIG. 1 is a cross-sectional view of a conventional optical module 10. As shown in FIG. 1, the optical module 10 includes a substrate 20, an optical waveguide 30, a luminous source 50, and an optical receiver 55. To the substrate 20, a lower wiring pattern 23 and an upper wiring pattern 27 are formed by patterning copper foils provided on the front and back surfaces of a base material 21. Further, the lower wiring pattern 23 and the upper wiring pattern 27 are electrically connected through a penetration via 22 formed in the base material 21. A solder resist 25 for protecting the lower wiring pattern 23 is arranged on the undersurface of the base material 21. The solder resist 25 has an opening at a position where a solder ball 26 is arranged, and the solder ball 26 that serves as an external connection terminal through the aperture is connected to the lower wiring pattern 23.
On the substrate 20 structured as described above, the optical waveguide 30, to which the luminous source 50 and the optical receiver 55 are connected, is fixed by adhesives 29.
FIG. 2 is an elevational view of the optical waveguide viewed in a direction A shown in FIG. 1. The optical waveguide 30 includes a lower clad layer 31, a core section 32, an upper clad layer 33, penetration vias 35, a device connection wiring pattern 39, a solder resist 41, and mirrors 45 and 46. The core section 32 is for transmitting an optical signal, and is formed on the lower clad layer 31. The upper clad layer 33 is formed on the lower clad layer 31 so that the core section 32 may be covered. Here, the refractive index of the material of the core section 32 is set up to be greater than the refractive index of the material of the lower and the upper clad layers 31 and 33.
The penetration via 35 is for electrically connecting the device connection wiring pattern 39 formed on the upper clad layer 33, and the upper wiring pattern 27 formed on the substrate 20. The solder resist 41 is prepared on the upper clad layer 33 for exposing a part of the device connection wiring pattern 39 where external connection terminals 51 and 56 of the luminous source 50 and the optical receiver 55, respectively, are connected, and for covering other parts of the device connection wiring pattern 39. Further, an optical entrance 42 for introducing the optical signal from the luminous source 50 to the core section 32, and an optical exit 43 for introducing the optical signal reflected by the mirror 46 to the optical receiver 55 are formed by the solder resist 41.
The mirrors 45 and 46 are formed in slots 57 and 58 that are formed in a V character shape from the side of the lower clad layer 31. The mirror 45 is for introducing the optical signal from the luminous source 50 into the core section 32. The mirror 46 is for reflecting the optical signal transmitted by the core section 32 so that it may reach the optical receiver 55. The optical signal introduced into the optical receiver 55 is converted to an electrical signal by the optical receiver 55. Further, after forming the mirrors 45 and 46, the slots are filled up with a clad material 47 serving as a reinforcing material.
Next, with reference to FIG. 3 through FIG. 7, a conventional manufacturing method of the mirrors 45 and 46 of the optical waveguide 30 is described. FIG. 3 through FIG. 6 show manufacturing processes of the mirrors, and FIG. 7 is an elevational view of the lower clad layer, the core section, and the upper clad layer looking in a direction of B shown in FIG. 3.
As shown in FIG. 3, the lower clad layer 31, the core section 32, and the upper clad layer 33 are formed one by one. Next, as shown in FIG. 4, the slots 57 and 58 in the shape of a V character dividing the core section 32 are formed by a dicer (dicing equipment) from the side of the lower clad layer 31. At this time, angles θ1 and θ2 between inclined planes 57a and 57b, respectively, and the undersurface 31a of the lower clad layer 31 are set at 45°, the inclined planes 57a and 57b being exposed by the slot 57. Further, angles θ3 and θ4 between inclined planes 58a and 58b, respectively, and the undersurface 31a of the lower clad layer 31 are also set at 45°, the inclined planes 58a and 58b being exposed by the slot 58.
Then, as shown in FIG. 5, a metal film is formed in the slots 57 and 58, and the mirrors 45 and 46 are formed on the inclined planes 57b and 58a, respectively. Then, as shown in FIG. 6, the clad material 47 serving as a reinforcing material is used to fill up the slots 57 and 58 (for example, Patent Reference 1).
[Patent reference 1] JPA, 2000-304953
[Description of the Invention]
[Problem(s) to be Solved by the Invention]
As described above, when conventionally manufacturing the optical waveguide 30, the V character-like slots 57 and 58 are formed from the side of the lower clad layer 31 that is pasted to the substrate 20, the metal film is formed in the slots 57 and 58, and the mirrors 45 and 46 are formed.
For this reason, the optical waveguide 30 cannot be formed in one body with the substrate 20, and a problem is in that the substrate 20 and the optical waveguide 30 have to be manufactured by separate manufacture processes.